Universal temperature calibrated pipette



Feb. 28, 1961 E. B. OFFUTT 2,972,889

I UNIVERSAL TEMPERATURE CALIBRATED PIPETTE v Filed July 18, 1956 2Sheets-Sheet 1 a Fig. 2

35 20" Fig. 3- [/40 l-NVENTOR E lmer Bradley Offuff BY 'varfl' ATTORNEYFeb. 28, 1961 E. B. OFFUTT UNIVERSAL TEMPERATURE CALIBRATED PIPETTEFiled July 18, 1956 2 Sheets-Sheet 2 I/WE/VTO/P. Elmer Bradley Offuffmagxm ATTORNEY UNIVERSAL TEMPERATURE CALIBRATED rrrnrrn Elmer BradleyOifutt, Independence, Mo., assignonto Standard Oil Company, tlhic'ago,Ill., a corporation of Indiana Filed .luly'18, 1956, Ser. No. 598,599

1 cnim. (c1. 73-4254 This invention relates to pipettes and, moreparticularly, to a calibrated pipette. g

It is frequently desired to deliver a given weight or standard volume ofa liquid Without the necessity of bringing such liquid to a standardtemperature prior to the pipetting operation and without the necessityfor making calculations to adjust the weight or volume to a standardtemperature. Heretofore it has been necessary to perform one or theother of these operations when it is desired to deliver such a standardquantity of liquid.

An example where such is to be desired is in connection with thedetermination of tetraethyl-lead in gasoline as described and claimed ina copending application v S. N. 165,164, filed May 31, 1950, jointlywith Leonard V. Sorg, now Patent No. 2,773,237, for Direct ReadingSystem for Metal Ion Determination, this application being acontinuation-in-part of said cop'ending application and of my copendingapplication S. N. 389,192, filed October 30, 1953, and entitledTemperature Calibrated Pipette, now abandoned.

Also, in ASTM Method D-526, for the determination of tetraethyllead ingasoline, there are requirements that the sample temperature measurementbe made in order to correct results to a sample volume of 60 F. (15.6C.). This can conveniently be done by means of my pipette graduated topermit measuring a sample equivalent in volume to a specified volume at60 F. (15.6 C.).

Pipettes employed in chemical and biological work include elongatedtubes of predetermined capacity and are used for drawing off a measuredquantity of liquid at ambient temperature from a vessel containing alarger quantity. Heretofore it has been necessary to correct theapparent volume by calculation or by adjusting the ac tua-l temperatureof the sample. This introduces errors and is generally not satisfactory.

An important object of my invention is, therefore, to provide a pipetteconstruction which will avoid the necessity for correcting a quantity ofliquid by calculation or adjustment of its temperature. A further objectof the invention is to provide a calibrated pipette which will deliver aknown quantity of liquid at a known temperature. Still another object ofthe invention is to provide a pipette which is temperature calibratedand which is universal in its application to aqueous and hydrocarbonliquids. become apparent as the description thereof proceeds.

The pipette, according to my invention, is not intended These and otherobjects of my invention will.

to eliminate the use of thermometers, but rather to avoid 2,972,889Patented Feb. 28, 1961 desired range. Merely knowing the temperature ofthe liquid permits accurate delivery of the standard quantity of liquidby filling the pipette to a level corresponding to the volume at thattemperature for the rated weight of liquid. Accordingly, the scale onthe stem is calibrated merely in degrees of temperature (Centigrade orFahrg enheit) and each degree mark represents the adjusted or correctedvolume of the standard quantity of liquid at the indicated temperature.

Further details and advantages of my invention will be described inconjunction with the accompaning draw: ings wherein: v p a Figure 1 isan elevation of a pipette employing my novel scale;

Figures 2 and 3 represents scales graduated for oil and waterrespectively; 5

Figure 4 is an enlarged View, partly in section, including a graduatedscale tube within a pipette stem;

Figure 5 is a fragmentary elevation including an cx ternal removablegraduated scale;

Figure 6 represents another embodiment of a scale tube which may beemployed in the pipette stems of Figures 4 and 5; and f Figure 7 is anadaptor tube for use with the removable scale and the pipette stern ofFigure 5 whereby differences in the coefficients of expansion arecompensated for to enable the use of a single pipette on either water orThe volume of liquid delivered by the pipette at the particulartemperature will be a volume adjusted in ac cordance with the prevailingtemperature so as to con tain the same amount of liquid material aswould be contained in a specified fixed volume at a specified fixedtemperature. For example, by the use, of the special pipette describedherein, a volume of gasoline having a temperature in the range ofbetween 15.6 C. and 3 5: C. can be measured, which volume will beexactly equivalent to a 50 ml. volume of the gasoline at 15.6 C. (60F.). Such a scale is illustrated in Figure 2.

Referring to the drawings, the lower end, or the end adapted to beplaced in the vessel containing the liquid, is drawn or beveled down toa reduced diameter sotthat the bore 13 therethrough is substantiallyless thanthe internal diameter of the discharge line'or tube 11 itsself.An enlargement in the tube itself provides a bulb or reservoir chamber10. The upper end' of the pipette comprises a tubular stem 12 ofrestricted diameter and open at its upper end. The liquid is drawn intothe pipette by placing the lower end of tube 11 in the vessel containingthe liquid and applying suction to the open end of the stem 12 of thepipette. The upper end of stem 12 is then closed by placing the fingerthereon and the relatively small diameter of the passage through thelower end 13 of the delivery tube 11 prevents any of the liquid fromrunning out of the pipette. V

Great care has been exercised in the manufacture of pipettes in order toproduce a relatively uniform inside diameter, and because of thedifiiculties involved in making an accurate pipette the expense thereofis relatively high. However, according to my inventionthe uppertranslucent stem 12 of the pipette is provided with a scale 14 whichindicates directly'the level of liquid in the stem necessary to'delivera standard quantity of the liquid at the ambient temperature.

The pipettes are ordinarily made to capacities of 10, 25, 50 and ml.Suitable scales 14 for the adjusted volumes for the rated capacity canbe devised for hydrov carbons and water knowing the data on the volumeof the pipette and inner diameter of the stem then referring to TablesI, II, III and IV.

3 Table I [50 m1. capacity, stem 5.7 mm. I.D.]

4 made possible by the conversion tubes 30 and 31 illustrated in Figures6 and 7. The internal diameter of the bore 32 in tube 31 of Figure 7 ischosen so as to com- Inches pensate for a relatively low thermalexpansion of water p., pl Int/Inch Inches Above as compared to thehydrocarbon. Thus by providing a Interval Interval Interval ig g scale33 corresponding to Figure 2 on a pipette stem 16 of Figure 4 or on thesleeve 25 of Figure 5 one may 4A M52 M72 0.65 M00 0,00 convert a pipettefor use in handling either oil or water. 2 8823 8-313 8-3 3 8 3g 8 Thusa pipette having the selected scale may be used 5 @1062 0:310 0:476 1for selecting a 50 ml. sample of gasoline at the ambient 5 0-062 0-3100-476 temperature, an extract of the gasoline is prepared according toASTM Method D526; and 50 mi. of the ex- A similar scale 14a for water inthe pipette can be tract can in turn be delivered into a polarographtitraderived as follows: tion apparatus employing the same pipette withan eX Table 11 Absolute Inches Temp., 0. Relative Volume, m1./ 0. m1./ml./Inch Inches Above Volume cc. Interval Interval 15.6 0.

Mark

1. 00097 0. 013 0. 057 0. e5 0 1. 00177 0. 013 0. 065 0. 65 0. 088 0.00 1. 00204 0. 01s 0. 065 0. 65 0. 100 0. 10 1. 00435 0. 013 0.065 0.650.100 0.20 1. 0050s 50. 0. 013 0.065 0. 05 0. 100 0. 39

I Page 1652 Handbook of Chemistry dz Physics, 29th edition.

Table III pension-compensated tube 31 such as shown in Figure 7 insertedinto the pipette stem. By this means a single Rated Pipette Capacity at150 0. scale designed for oil can be used on the aqueous extract asWell, the decreased internal diameter of the com- 50 ml. 100 ml. 25 ml.pensating tube 31 serving to magnify the volume changes corresponding tothe ambientiternperature. bus 0. Although I have described the inventionin terms or" 9 22 examples set forth in some detail, it should be under-0.065 stood that these are by way of illustration only and that 0-080the invention is not limited thereto. Alternative embodiments willbecome apparent to those skilled in the art in view of my description ofthe invention, and accordingly it it contemplated that modifications maybe made Rated Pipette Capacity at 15.6 C. in the invention withoutdeparting from the spirit thereof.

What I claim is: 501111. 100ml. 25:01. In pipette for use in determiningthe tetraethyllead content in gasoline, and of the type having a liquidStem,mm. 1.1).: 11t./5 0. 17L./5 0. Ira 5 0. reservoir chamber, adischarge line depending from said 5 352 1353 3: chamber, a verticallyextending stem axially aligned with 0. 912 1.238 0.309 and carried bysaid chamber and having a bore through 534 0'383 said stem, said liquidreservoir chamber, said discharge line, and said vertically extendingstein being in fluid I Refenlhg to Flghre 4, the Stem 16 011 P p 113Vcommunication, and an index mark on said vertically exmg a bulb ofreservoir Chamber enlarged to acorn tending stem indicating thedelivered volume of a liquid modate the insertion of Scale tube 13 toProvide a at a standard temperature, the improvement whereby tinuationof the stem 16 having substantially the same inh pinette is capable 0fdelivering, at a plurality of ternal diameter. resilientsleeve 19 Sec rthe Scale peratures, either water or gasoline, said gasoline having a h18 m the deslred Posltloh Within the Stem h difierent coefficient ofexpansion from Water, which coni- Wln be understood that the bench mark29 for prises a single replaceable sleeve insertable arounr. said on thetwo Scales 21 and 22 an? aligned with the bench vertically extendingstem and alignable with said index mark 5 0n the Stem mark, and twograduated scales on said sleeve calibrated I11 Flglll'e 5 the Scales q24 are Carried y a in degrees of temperature, the first scale indicatingthe movable P Sleeve 5 h h 1S transparent and which delivered volumes ofwater over a range of temperatures h a base mark 26 Whlch 1S ahghed Withthe coffespOhdequivalent to the delivered volume of water at thestandll'lg hottolh malk 27 fepfesehtlhg GII the Stem ard temperature,and the second scale indicating the P of Pressure Sensitive adhesive 29y be delivered volumes of gasoline over a range of temper- P to preventan unintentional relocation of the atures equivalent to the deliveredvolume of gasoline at sleeve 25 along the length of the stem 28.Ordinarily the standard temperature the sleeve will be constructed ofthin clear plastic matemil which frrctionally engages the exterior ofthe stern References Cited in the file of this Patent 28. It 18 alsocontemplated, however, that a number of plerforations of substantialarea may be provided in the UNITED STATES PATENTS s eeve 25 removed fromthe scales 23 and 24- so that res- '1 I 1 Sure sensitive adhesive tapemay be Wrapped b i h 7 Homstead 1f; sleeve 25 and contact the stem 23through the erfgra- 1390553 Hassinger 191) fions P 1,355,970 HassrngerOct. 19, 1920 1,386,571 Jackson Aug. 2 1921 It 1s also desired toprovide a pipette wherem a single 1 533 753 M n 1 A P P B having aSingle scale may be employed for sam lu C 1 mg of both hydrocarbon andaqueous liquids. This is (Other references on following page) 5 6FOREIGN PATENTS tion by Central Scientific Co., Chicago, 111., 1927,pages 322,864 G J 1 10, 1920 ermany u y Laboratory Apparatus andReagents, publication by OTHER REFERENCES Fisher Scientific Co.,Pittsburgh, Pa., 1926, page 495.

Providing for Changes in Temperature in Volumetric 5 Ace General Catalog40, publication by Ace Glass Analysis, by Mellon, Analytical Chemistry(formerly Inc. Vineland, N.J., 1940, page 135. published under the titleof Industrial and Engineering Selected Laboratory Equipment, Catalog No.50,

Chemistry, Analytical Edition), July 15, 1930, vol. 2, publication byShaar & Co., Chicago, 111., pages 539 and N0. 3 (pp. 260 to 263). 551.

Laboratory Apparatus, Catalog C. No. 227, publica- 10

